The gear coupling is composed of parts such as an inner gear ring with the same number of teeth and a flanged half coupling with outer teeth. The outer teeth are available in two types: straight teeth and drum-shaped teeth. The drum-shaped teeth refer to the outer teeth being shaped into a spherical surface, with the center of the sphere on the gear shaft axis, and the tooth side clearance being larger than that of general gears. Drum-shaped gear couplings can allow for greater angular displacement (compared to straight teeth couplings), can improve the contact conditions of the teeth, enhance the ability to transmit torque, and extend the service life.